(1) Field of the Invention
The present invention relates to a non-oriented electrical steel sheet, and more particularly relates to a cold rolled non-oriented electrical steel sheet having a low iron loss.
(2) Description of the Prior Art
Non-oriented electrical steel sheets are graded by their iron loss. For example, in the JIS, non-oriented electrical steel sheets having a thickness of 0.050 mm are graded as follows. In the S-30 grade steel sheet, W.sub.10/50 must be not higher than 3.70 W/kg and W.sub.15/50 must be not higher than 8.00 W/kg; and in the S-10 grade steel sheet, W.sub.10/50 must be not higher than 1.25 W/kg and W.sub.15/50 must be not higher than 3.10 W/kg.
The iron loss of non-oriented silicon steel sheets is occupied by the hysteresis loss rather than by the eddycurrent loss contrary to the iron loss of oriented electrical steel sheets, and the hysteresis loss occupies generally 60-80% of the total iron loss. The hysteresis loss is in inverse proportion to the crystal grain size. It is an effective means to promote the normal grain growth of recrystallized grains at the final annealing in order to decrease the iron loss, and this means has hitherto been always used in order to lower the iron loss.
The inventors have newly found out that the alloying of Sn to non-oriented silicon steel sheet is effective for lowering the iron loss thereof, and have accomplished the present invention.